The present invention relates to a phase change memory device and a method for manufacturing the same, and more particularly, to a phase change memory device which can prevent thermal crosstalk and a method for manufacturing the same.
In the semiconductor industry, a study has been directed toward developing a novel memory device having a simple configuration and being capable of accomplishing a high level of integration while retaining the characteristics of a non-volatile memory device. For example, a phase change memory device.
In the conventional phase change memory device, a a phase change layer is interposed between a bottom electrode and an upper electrode. The phase change layer changes from a crystalline state to an amorphous state according to current flow between the bottom electrode and the upper electrode. The information stored in a cell is recognized according to the difference in resistance between the crystalline state and the amorphous state of the phase change layer.
As semiconductor devices become more highly integrated, the size of the phase change memory device gradually decreases as does the size of a thin film for heaters (hereinafter, referred to as “heaters”), which contact the phase change layer and serve as one of the electrodes directly influencing the change of the crystalline state of the phase change layer.
When the size of the heaters decreases as described above, the heaters cannot be formed to have a uniform size and are therefore formed non-uniformly. As such, the distribution of programming current necessary for the phase change of the phase change layer will also become non-uniform.
Further, as the size of cells is reduced, in the case of a phase change memory device, which utilizes micro holes, thermal crosstalk is likely to occur when programming the cells. Such thermal cross talk is an undesired phase change phenomenon caused by thermal influence from adjoining cells.
The thermal crosstalk can change the data of the cells or cause partial phase change in the cells, which results in the deterioration of the sensing margin of the phase change memory device. This occurs, for example, when the thermal crosstalk is of a temperature sufficient to change the phase change state of a neighboring cell.